1. Field of the Invention
This invention relates to longwall mining machinery, and in particular, to improvements to a longwall mining machine of the type having a pivot arm which supports a cutter drum for rotation about an axis for working a mine face. In a mining machine of this type, the rotating cutter drum, which carries cutting bits on its outer periphery, is provided with spirals which assist in loading the mined material onto a face conveyor.
2. Description of the Prior Art
In U.S. patent application Ser. No. 288,037, filed July 29, 1981, there is described a cutter drum, in equipment of the type indicated above, which has a nozzle holder disposed at the back of the cut. The object of the invention of this earlier application is to show the possibility of reducing the dust evolution, which is particularly high at the back of the cut when minerals are mined by means of a cutter drum. The above-mentioned application solves the problem of reducing dust evolution by providing equipment of the kind indicated above, wherein the nozzle holder is mounted on the cutter drum shaft so as to be relatively non-rotatable and of symmetrical construction with respect to rotation. Moreover, the nozzle holder is dimensioned at least so as to correspond to the diameter of the drum body, and it is equipped with nozzles which are distributed over its periphery and form two groups, only one of which is adapted to be fed when the direction of travel of the mining machine is in one direction, while the other group is adapted to be fed only while the direction of travel of the mining machine is in the other direction. The nozzles direct a spray onto the mineral needing to be loosened, said spray pattern extending over the height of the drum. By means of the high-pressure liquid jets leaving them, the nozzles comminute, without any dust evolution, that part of the seam which projects in front of them. The part of the seam located in back of the cut is particularly hard. The nozzles insure that the drum is cut free, as is required, in this zone. With such apparatus, however, the efficiency of the high-pressure water jets leaving the nozzles is impaired, because the water flowing away from the impact area of the jet destroys some of the energy of the impinging high-pressure jet and thus reduces its efficiency.
Cutter drums for mining machines are known which have a conical end ring at the back of the cut, and the end ring bears pick holders which are distributed over its periphery and contain picks which project beyond the drum's end face and cut it free (German Offenlegungsschrift No. 27 22 450).
An object of the present invention is to obviate this defect and to provide direct contact between the mineral needing to be loosened and the high-pressure liquid jet which impinges on this mineral, such contact being unobstructed by the discharged water.